Patients undergoing radiation therapy are typically placed on a treatment platform of a radiation treatment gantry. The gantry has a radiation source that is used to generate a radiation beam that irradiates a region of interest in the patient, such as diseased tissue including a tumor or cancerous growth site. Although the radiation can reduce the amount of diseased tissue, it can also have a harmful effect on the healthy tissue surrounding the diseased tissue. Thus, it is generally desirable to deliver the lowest effective dose of radiation localized with respect to the targeted tissue.
When delivering the radiation, a plurality of beams of radiation may be directed to the target area of interest from several positions outside the body. The gantry can be rotated to provide the radiation beams from different positions. The point at which the beam trajectories converge or intersect is generally referred to as the isocenter. The isocenter typically receives the largest radiation dose because of the cumulative radiation received from multiple radiation beams.
Conventionally, an image guided radiation therapy (IGRT) system generally uses an image of a patient to choose a location for the treatment plan isocenter. The patient is positioned in the treatment device based on image information and the isocenter of the machine. The dose received by the patient at the isocenter can be estimated by measuring the radiation dose in a phantom device. Some phantom devices may be configured to simulate radiation exposure of the body, for example, by using a solid or liquid material that mimicks the composition of the body, and may include dosimeters for determining a radiation dose at and around the isocenter.